Issue #13795 has been updated by davidarnold (David Arnold).
ruby -v set to ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]
> This might make the next version of Ruby not backwards-compatible in some instances. It might be better to leave the methods as they are.
Ruby has been not backwards-compatible in several releases, so I don't see that as a reason per se to not entertain the two proposals. I do agree with you that the documentation and tests should be improved if the decision is made to leave things as-is.
My speculation is that the custom functionality of Hash#select was very useful when it was introduced in 1.9, as Array#to_h did not exist yet. However with 2.1, when to_h became an option, the disjointed behavior became less useful, and more of an inconsistency.
~~~ ruby
h.select {|k,v| k > "a"}.to_h
# vs
h.select {|k,v| k > "a"} # did this really save that much effort?
~~~
I feel like breaking the contract of Enumerable#select is bad, but I will fully admit that Hash#select returning a Hash is probably a very popular feature!
Either way, back to the topic of the bug, I am not sure why find_all was left behind through all this.
----------------------------------------
Bug #13795: Hash#select return type does not match Hash#find_all
https://bugs.ruby-lang.org/issues/13795#change-66114
* Author: davidarnold (David Arnold)
* Status: Open
* Priority: Normal
* Assignee:
* Target version:
* ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
Enumerable#select and Enumerable#find_all are aliases. Hash is_a Enumerable, yet only Hash#select was overridden to return a Hash, with Hash#find_all still returning an Array. This is confusing since the message is that you can use select and find_all interchangeably for Enumerable, yet when you get to Hash, there are warnings that it is no longer true.
Also any code that expects to call select on an Enumerable and get an array back (as documented) could break, but only for Hash#select.
Example:
~~~ ruby
def select_many(*enumerables, &block)
result = []
enumerables.each do |e|
result.concat e.select(&block)
end
result
end
select_many([1, 2], [3, 4]) { |x| x % 2 == 0 } #=> [2, 4]
select_many({ 1 => 2 }, { 3 => 4 }) { |k, v| k < 2 } #=> TypeError: no implicit conversion of Hash into Array
~~~
Should Hash#find_all also return a Hash for consistency? Or, given the fact that calling #to_h on the resulting Array is so easy, should Hash#select revert to the Enumerable behavior of returning an Array?
Proposal 1:
~~~ ruby
h = { "a" => 100, "b" => 200, "c" => 300 }
h.find_all {|k,v| k > "a"} #=> {"b" => 200, "c" => 300}
~~~
Proposal 2:
~~~ ruby
h = { "a" => 100, "b" => 200, "c" => 300 }
h.select {|k,v| k > "a"} #=> [["b", 200], ["c", 300]]
h.select {|k,v| k > "a"}.to_h #=> {"b" => 200, "c" => 300}
~~~
--
https://bugs.ruby-lang.org/
Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>